Thai Chicken and Coconut Milk Soup

Name: Thai Chicken and Coconut Milk Soup
Ingredients: 6 cups chicken stock; Zest of 3 large limes; Zest of 3 large lemons; 6 heaping tablespoons coarsely chopped fresh ginger root; 3 hot green chiles, halved and seeded (preferably jalapeno); 3/4 cup chopped cilantro stems and roots, washed carefully; 3/4 pound boneless, skinless chicken breast, half-frozen; 3 tablespoons lime juice; 1 tablespoon sugar; 1 tablespoon Nam Pla, bottled Thai fish sauce; Finely chopped scallion and cilantro leaves, for garnish